Wire antennas for listeners
How to install a wire antenna ? (IV)
After have seen characteristics of a "good" antenna in terms of length and height above ground and explained how to select an antenna and use a long wire indoor or on the balconery, let's see how we can easily install a wire antenna outdoor. This chapter is mainly dedicated to listeners who cannot necessary install a beam, a quad or a large vertical in their backyard. Here are some suggestions.
You can for example run your wire antenna made of stranded steel wire (or solid copper wire) from your receiver to the last tree at the far end of your garden in straight line and attach its end around a strong branch. But it is not mandatory that the path is straight or the end insulated as that can be for a transmitting antenna. The wire can be turned around one of two trees without problem to make an area antenna in shape of "U" if you want or it can be tight in zig-zag (Z-shape) to avoid big trees. You can also hang it below the gutter of your house to keep it out of sight and from there run a dark colored wire to the roof of your cottage located some dozen meters away.
Some QSLs received by the author
If your free space is very limited or if you want a discrete and stealth installation, the wire can run along a high fence or be hanged along the building external wall. Of course in these two latter cases your S-meter will drop a bit. You can also suspend your long wire in inverted-V (L), placing the center top as high as possible in a tree, its ends stopping near the ground, the two segments forming a wide angle (about 120°) to increase directivity and reduce QRM. At last you can slope the long wire at 45°; tight it between the house 2d floor or the chimney and an insulator fixed on a remote anchor point (fence, tree, wall, etc). Do not forget to place an indicator or some plants around your anchor point to avoid accidents.
For a receive wire antenna, the fact to cross an orchard 3m high, touching a roof or be near a metallic container is not as important as it is for emitting. However know that your antenna can couple with these metal surface and pickup more QRM.
Another suggestion : rust and multiple wires constitute as many as antennas. So use only wire in good state, and a steel cable protected with PVC offers here a good solution.
As we told previously, if you have to attach several wire segments together, plait the ends together then solder the junction and attached along this section two mini-clamps in order that both wires cannot be released. Then pull strongly on the wire to test its resistance.
For an electrical length of 1/2l or 1/4l the fact to turn the wire antenna in various directions will not privilege one or another continent because at these lengths this antenna displays a cylindrical radiation pattern along its axe that closes to the ends; it is omnidirectional. As we explained in various other pages including the ones dealing with the G5RV dipole, the directivity is only improved with antennas placed over 8-10m high, with Beverage antennas longer than 160 m (over 8l for the 20m band) suspended 2 m high or if you place a vertical segment of about 7 m at the end of your wire, itself already placed quite high.
On the other side the wire tilt changes the reception and therefore the fact to attach one segment of your wire much higher than the other one (e.g. 5m higher than the other end) improves the reception in some direction as is the fact to install the wire in inverted-V (L) if you use a length of at least 2x 20 m and if you can attach the centre part of the antenna at about 8-10 m high, the ends being near ground level.
Some other QSLs received by the author
Sometimes personal computers emit strong RFI in ham bands. So if the case arises, avoid to use your portable computer while your receiver is switched on or you will hear severe QRM (up to exceed several dB over S-9) mainly in the 40-10m bands induced by the keyboard, the AC adapter (or any battery charger powered) or LEDs. Modern desktop computers seem much better protected against these electromagnetic emissions although the mouse, the transformer and the display (CRT or plasma) produce some interferences if your RX is nearby. In that matter know that RFI decrease as the square of the distance. On the other side, if you cannot move your equipment the use of double shielded power lines and a separate electrical circuit for all domestic devices is often the solution to remove RFI. The use of some electromagnetic accessories like chokes on power lines can also help in solving or at least reducing this problem. If you need more information I suggest you to read the page about RFI, troubles and solutions.
To convince you how easy and fine can be a so light installation, practically to get all SWL QSLs displayed on the dedicated pages, in the 80's I have no shame to say that I installed in Brussels (20 km off center) a 2x 20m long "TV" coax cable (75 ohms, the only electric wire I had at that time) forming an horizontal-V opened at ~ 45° that I placed on top of a 3-story building, on a roof made of armed concrete and covered with asphalt, one leg end of the wire antenna running along the external wall on about 15 m to the receiver, the braid being not connected to the ground. This configuration, although it was not tuned at all and captured much QRM, allowed me to hear over 100 DX entities from 5 continents in a few months, including KL7, ZS and ZL ! Since that time I bought a better RTX and new antennas to improve the selectivity of weak signals but for a while I continued to work with a dipole that gave me excellent results, far better than any vertical antenna.
For making tests, I installed on the heights of Wépion, Belgium a Fritzel GP-404 ground plane multi-band vertical (6m high with 2 traps and 1 flexible radial per band) to work on the bands from 40-10m and a G5RV multi-band dipole that gave both very good results although the dipole picked up less QRM than the vertical. A Wellbrook active magnetic loop ALA-1530 was also installed for listening purposes. This second installation using an indoor antenna performed however not as good as the dipole installed outdoor but it did when it was placed beside it. Indeed, both are wire antennas, working in a horizontal polarization (fed by the center base) and displayed a similar gain.
And why not a beam ?
In the case of you want to erect a vertical antenna above ground, or a directive antenna, you will have first to answer the next questions :
- Does the municipality or cadastre of my town allow such a building, and up to what height and sizing ?
- How to erect a tower 10m high or higher (using a telescopic mast, a crane, with the help of friends, etc) ?
- How to ensure the stability of the tower (using a free-standing tower or attaching guy wires to the tower) ?
- How to place the antenna and the rotator on top of the pylon (using a gin-pole, a tilting the base, a lift, a crane, etc) ?
With so much "difficulties" to solve for a beginner (even for a licensed amateur who makes this choice maybe once in his ham life), it is far easier to begin with a lighter installation, all the more that erecting a tower in your garden and installing a beam on top is rather expensive when you count all required accessories (do not forget securities issues, the rotator and cabling system).
So I suggest you to review these light installation taking advantage of wire antennas. They are much cheaper than any array antenna (beam, quad) and of course much easier to install.
Of course if you realy want to erect a pylon in your backyard, this is not a problem. You can do it with friends used to work on towers and handling antennas or entrust this work to a specialized company. Be only prepare to invest a lot of money and much time.
About matching box
To get the best results an end- or central-fed wire antenna (long wire, Windom, Levy, and even sometime a dipole) or a rod aerial should be matched to the receiver input circuit with an antenna coupler or an aerial tuning unit.
It is not mandatory as long as you can get a high efficiency (in transmission we should say a low SWR). In all other circumstances you need to insert a matching network or use an external antenna tuner unit, the famous A.T.U to match impedances. This unit includes an inductor made of some tens of turns of insulated wire wound on an insulated cylindre, the loops being soldered to switch tags.
Each tuning capacitor is then calibrated with a knob and switched positions are numbered. Practically you adjust the capacitors and the wafer switch position to get the maximum signal strength knowing that the three adjustements are very much interdependent.
One of the cheapest manual matching box is the Yaesu FRT-7700 (60 €) displayed at right. This device provides inputs for simple copper wires and for a PL-connector and supports up to 100 W PEP.
If the antenna has the correct size, its physical length is in resonance with the voltage and current, then the tuner is useless. Most modern receivers provide a built-in antenna tuner as well for the fine tuning (inside a specific band and below SWR 2.5:1 or so).
Remember that if your antenna is not properly cut for each band and matched to your transceiver impedance, without ATU you have a chance to experiment signal loss and therefore to alter your antenna radiation pattern. Worse, if you try to transmit with an untuned antenna system, you will get a very high SWR (over 4:1), much RF losses and all chance to burn your transceiver PA.
By way of conclusion
Remember always that there is a huge difference between the needs of a licensed amateur and the ones of a listener. For listening purposes what differenciates antennas is not the model - vertical, wire or beam - as there is no major differences from what you hear with each of them, but rather their length from which depends their ability to pick up weak signals, and in a lesser extent their position in respect to buildings and parasitic wires or plumbing (the farest the best to reduce QRM and avoid electric coupling).
For receiving purposes as well for transmitting, take care to the angles of takeoff of your antenna. You will discover that there are some difference placing your antenna low (2-6m) or high (7-20m) over the ground, mainly listening to weak DX stations. In fact when powered your antenna reacts much against ground effects (resistivity, capacitance, etc) and at very low heights its radiation pattern becomes quasi omnidirectional with the main lobe close to 90°.
If you are looking for a low cost receive antenna, the cheapest but performing installation is a long wire 20 or 40m long tight as high as possible above ground (over 10m for the 20-m band). Believe me, in a few hours you will hear many DX stations, except the weakest ones located over 10,000 km away. This is already a performance !
A Swissdipole 11m (37ft) long.
Then try to build for a few euros or to buy for about 80-100 euros a true multi-band dipole (e.g. a G5RV or a W3DZZ 30m long) or a 20 or 40m long Carolina Windom; you will capture very few QRM but many hams and DX-peditions, sometimes located 20,000 km away by the long path !
The other solution is to erect a simple ground plane vertical 6 or 8m high on the roof or a few meters above the ground. If you really lack of space but have some money left, the active magnetic loop is another solution very appreciated.
For short, for listening purposes there is only one rule : the greatest is the length of the antenna and higher it is installed, the better you will receive distant and weak stations. So that means that your antenna should preferably be installed outdoor.
Of course none of these "small guns" can fight against the "power of fire" of a beam or a quad that displays easily a gain over 10 dBd placed 15m high, and even twice as much using numerous directors, with a front-to-back ratio exceeding 20 dB.
To end this chapter I remind you that once powered by your receiver, your antenna constitutes an electric circuit. If it is not grounded and is badly protected, it can offer an excellent path to lightning and electromagnetic induction, in direct way to your receiver and all your electrical equipment, including your phone and all your peripherals... So, in leaving this page I suggest you to read all about lightning protection before proceeding to your installation. If you don't want to make this installation, as soon as you hear the thunder approaching don't forget to disconnect your antenna coaxial cable from your receiver and all your electrical equipment from the main. Better be warn than paying the bill, Hi !
For more information
Basics of Antennas (on this site)
eHam reviews (specially Antennas)
ARRL Antenna Book, ARRL (specially chapter 16)
ARRL Antenna Book 1998 in PDF, QRZ.ru
Small Antennas for Small Spaces, ARRL, 2011
Vertical Antenna Classics, ARRL, 1995/2001.